Ed Miliband has pledged that a Labour government would significantly increase the national minimum wage over the course of the next Parliament by linking it to average earnings.

In a speech to party activists in the West Midlands, the Labour leader said the measure would ensure the lowest-paid did not get "left behind" again.

He said the move to establish a clear link with average earnings would help build on the Labour government's achievements in introducing the minimum wage following Tony Blair's landslide 1997 general election victory.

Business groups are expected to criticise Mr Miliband's announcement

The announcement will be welcomed by those in the party who say Mr Miliband has yet to offer voters a positive vision of what they could expect from a Labour government.

But the move is also likely to face criticism from the business world and prompt claims it will harm competitiveness.

Mr Miliband described Labour's introduction of the minimum wage as "one of the proudest achievements of any British government", but said further action was now needed to raise its value.

"Britain is still one of the lowest paid countries among the world's advanced economies," he said.

"So we have to go further, we have to write the next chapter in the history of Labour's battle to make work pay.

"That's why today, I am proud to announce that the next Labour government will take new radical action against low pay: a new five-year ambition to restore the link between doing a hard day's work and building a decent life for your family.

"A Labour government will establish a clear link between the level of the minimum wage and the scale of wages paid to other workers in our economy.

"We will say workers on the minimum wage must never be left behind because those who work hard to create our nation's wealth should share in it."

But details of the policy were lacking in his speech, and low-pay campaigners will want to see exactly how a Labour government would go about fulfilling its goal.

However, Mr Miliband will publish a report he commissioned from Alan Buckle, the former deputy chairman of KPMG International, with proposals to overhaul the Low Pay Commission.